Method of forming contacts for a memory device

ABSTRACT

The present invention is generally directed to a method of forming contacts for a memory device. In one illustrative embodiment, the method includes forming a layer of insulating material above an active area of a dual bit memory cell, forming a hard mask layer above the layer of insulating material, the hard mask layer having an original thickness, performing at least two partial etching processes on the hard mask layer to thereby define a patterned hard mask layer above the layer of insulating material, wherein each of the partial etching processes is designed to etch through less than the original thickness of the hard mask layer, the hard mask layer having openings formed therein that correspond to a digitline contact and a plurality of storage node contacts for the dual bit memory cell, and performing at least one etching process to form openings in the layer of insulating material for the digitline contact and the plurality of storage node contacts using the patterned hard mask layer as an etch mask.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 12/892,684, filed Sep. 28, 2010, entitled “Methodof Forming Contacts for a Memory Device”, naming Jonathan Doebler asinventor, which resulted from a divisional of U.S. patent applicationSer. No. 11/368,898, filed on Mar. 6, 2006, entitled Method of FormingContacts for a Memory Device”, naming Jonathan Doebler as inventor, nowU.S. Pat. No. 7,807,582 B2, the disclosures of which are incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of The Invention

The present invention is generally related to the field of manufacturingintegrated circuit devices, and, more particularly, to a method offorming contacts for a memory device.

2. Description of the Related Art

Memory devices are typically provided as internal storage areas in thecomputer. There are several different types of memory. One type ofmemory is random access memory (RAM) that is typically used as mainmemory in a computer environment. Most RAM is volatile, which means thatit requires a steady flow of electricity to maintain its contents.

A dynamic random access memory (DRAM) is made up of memory cells. Eachcell of a modern DRAM includes a transistor and a capacitor, where thecapacitor holds the value of each cell, namely a “1” or a “0,” as acharge on the capacitor. Because the charge on a capacitor graduallyleaks away, DRAM capacitors must be refreshed on a regular basis. Amemory device incorporating a DRAM memory includes logic to refresh(recharge) the capacitors of the cells periodically or the informationwill be lost. Reading the stored data in a cell and then writing thedata back into the cell at a predefined voltage level refreshes a cell.The required refreshing operation is what makes DRAM memory dynamicrather than static.

Referring to FIG. 1, a schematic diagram of an illustrative DRAM memorycell 10 is depicted. The cell 10 is illustrated as having a capacitor 12and an access transistor 14. The capacitor 12 is used to store a charge.The charge represents a bit of information. The access transistor 14acts as a switch for the capacitor 12. That is, the access transistor 14controls when a charge is placed on the capacitor 12, and when a chargeis discharged from the capacitor 12. A word line 16 is coupled to acontrol gate of the access transistor 14. When a cell is read, the wordline 16 activates the control gate of the transistor 14. Once thishappens, any charge (or lack of charge) stored on the capacitor 12 isshared with a conductive digitline 18 coupled to the drain of the accesstransistor 14. This charge is then detected in the digitline 18 by asense amplifier (not shown) and then processed to determine the bitstate of the cell 10. Tiling a selected quantity of cells 10 together,such that the cells 10 along a given digitline 18 do not share a commonword line 16 and the cells 10 along a common word line 16 do not share acommon digitline 18, forms a memory array. A typical memory arraycontains thousands or millions of cells 10.

A simplified block diagram of a prior art DRAM 20 is described in FIG.2. The memory device can be coupled to a processor 32 for bi-directionaldata communication. The memory includes an array of DRAM memory cells22. Control circuitry 28 is provided to manage data storage andretrieval from the array 22 in response to control signals from theprocessor 32. Address circuitry 26, X-decoder 26 a and Y-decoder 26 banalyze address signals and storage access locations of the array 22.Sensing circuitry 24 is used to read data from the array 22 and coupleoutput data to I/O circuitry 30. The I/O circuitry 30 operates in abi-directional manner to receive data from the processor 32 and passthis data to array 22. Of course, those skilled in the art willunderstand that the illustrative circuitry depicted in FIG. 2 does notinclude all of the circuitry of a functioning DRAM.

The manufacture of memory devices, particularly DRAMs, is a verycompetitive industry. Thus, process engineers are faced with continuouspressure to become ever more efficient in the processing techniques andmethods used to form such devices. In general, manufacturing a DRAMdevice involves the performance of many individual process steps. Forexample, multiple deposition, cleaning, etching, ion implantation,polishing and heating processes are typically performed in a preciseorder to produce a DRAM device. Such processes typically involve the useof very complex processing tools that are very expensive to maintain anduse.

During the formation of memory devices, several conductive connectionsmust be made to device features formed in and above a semiconductingsubstrate. Conductive connections that couple a conductive metal line toa device formed in or above the substrate, or ones that are coupled tothe substrate itself are sometimes referred to as contacts. Conductiveconnections between layers of conductive lines that are positioned inlayers of insulating material are sometimes referred to as vias. Forexample, in a DRAM array 22 having a dual bit memory cell structure, aso-called digitline contact is provided between a digitline and anaccess device, e.g., a transistor, formed in or above a substrate.So-called storage node contacts are formed between the access transistorand a capacitor or storage node where electrical charge may be stored.Additionally, there are many contacts that must be formed to othersemiconductor devices, e.g., transistors, resistors, capacitors, thatare used to form contacts in areas of the DRAM outside of the memoryarray 22. For example, contacts must be formed to the semiconductordevices that comprise the sensing circuitry 24 as well as other circuitslocated outside of the array 22, i.e., the non-array circuitry.

In a typical process flow used to form a DRAM, contacts formed withinthe array 22 are formed at a different time relative to the formation ofcontacts to circuits outside of the array 22. Thus, although the precisemethodology of forming the contacts may involve similar steps, theprocess steps are performed at different points in time during thecourse of manufacturing the device. Additionally, the formation of adigitline contact and the storage node contacts is generally formed byperforming a sequence of process steps that typically involves severalpolishing steps wherein an upper surface of the gate electrode for theaccess transistor is used as a polishing stop surface in a chemicalmechanical polishing (CMP) process. Since the upper surface of the gateelectrode is frequently covered with a layer of silicon nitride (a“nitride cap”), such processing steps are sometimes referred to asstop-on-nitride (SON) polishing techniques. In the case of a DRAM with aburied access device, CMP processes may lead to dishing within the array22 which, in turn, may lead to problems with future photolithographyprocesses. When performing such a CMP process on a DRAM with non-buriedaccess devices, it is generally preferable to remove the nitride cap onthe gate electrodes outside of the array 22 by using a photolithographystep to protect the array 22. Typically, contacts inside the array 22are filled with polysilicon and contacts outside of the array 22 arefilled with a metal, such as tungsten.

What is needed is a more efficient methodology for forming contacts onDRAMs. The present invention is directed to a device and various methodsthat may solve, or at least reduce, some or all of the aforementionedproblems.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an exhaustive overview of the invention. It is notintended to identify key or critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts in a simplified form as a prelude to the more detaileddescription that is discussed later.

The present invention is generally directed to a method of formingcontacts for a memory device. In one illustrative embodiment, the methodcomprises forming a layer of insulating material above an active area ofa dual bit memory cell, forming a hard mask layer above the layer ofinsulating material, the hard mask layer having an original thickness,performing at least two partial etching processes on the hard mask layerto thereby define a patterned hard mask layer above the layer ofinsulating material, wherein each of the partial etching processes isdesigned to etch through less than the original thickness of the hardmask layer, the hard mask layer having openings formed therein thatcorrespond to a digitline contact and a plurality of storage nodecontacts for the dual bit memory cell, and performing at least oneetching process to form openings in the layer of insulating material forthe digitline contact and the plurality of storage node contacts usingthe patterned hard mask layer as an etch mask.

In another illustrative embodiment, the method comprises forming a layerof insulating material above an active area of a dual bit memory cell,forming a hard mask layer above the layer of insulating material, thehard mask layer having an original thickness, performing at least twopartial etching processes on the hard mask layer to thereby define apatterned hard mask layer above the layer of insulating material,wherein each of the partial etching processes is designed to etchthrough less than the original thickness of the hard mask layer, thepatterned hard mask layer being comprised of a material that isselectively etchable with respect to the layer of insulating material,the patterned hard mask layer having openings formed therein thatcorrespond to a digitline contact and a plurality of storage nodecontacts for the dual bit memory cell, and performing a single etchingprocess to form openings in the layer of insulating material for thedigitline contact and the plurality of storage node contacts using thepatterned hard mask layer as an etch mask.

In yet another illustrative embodiment, the method comprises forming alayer of insulating material above an active area of a dual bit memorycell, depositing a hard mask layer above the layer of insulatingmaterial, the hard mask layer having a deposited thickness, performingat least two partial etching processes on the deposited hard mask layerto form a patterned hard mask layer, wherein each of the partial etchingprocesses is designed to etch through less than the entire depositedthickness of the hard mask layer, the hard mask layer having openingsformed therein that correspond to a digitline contact and a plurality ofstorage node contacts for the dual bit memory cell, and performing atleast one etching process to form openings in the layer of insulatingmaterial for the digitline contact and the plurality of storage nodecontacts using the patterned hard mask layer as an etch mask.

In a further illustrative embodiment, the method comprises forming alayer of insulating material above an active area of a dual bit memorycell, forming a patterned hard mask layer above the layer of insulatingmaterial, the patterned hard mask layer being comprised of a materialthat is selectively etchable with respect to the layer of insulatingmaterial, the hard mask layer having openings formed therein thatcorrespond to a digitline contact, a plurality of storage node contactsfor the dual bit memory cell and an opening for a contact located in aperipheral circuit located outside of a memory array comprising the dualbit memory cell, and performing a single etching process to formopenings in the layer of insulating material for the digitline contact,the plurality of storage node contacts and the contact for theperipheral circuit using the patterned hard mask layer as an etch mask.

In yet a further illustrative embodiment, the method comprises forming aplurality of word line structures, forming a digitline contact, at leasta portion of which is positioned between the word line structures,forming a plurality of storage node contacts, each of which comprises aportion that is positioned between one of the word line structures and apassing word line structure, and forming a liner comprising a low-kdielectric material having a dielectric constant less than 7 adjacent atleast a portion of a side of each of the storage node contacts.

In still a further illustrative embodiment, the method comprises forminga plurality of word line structures, forming a digitline contact, atleast a portion of which is positioned between the word line structures,forming a plurality of storage node contacts comprising a unitaryconductive structure, each of the storage node contacts comprising aportion that is positioned between one of the word line structures and apassing word line structure, and forming a liner comprising a low-kdielectric material having a dielectric constant less than 7 adjacent atleast a portion of a side of the unitary conductive structures.

In still another illustrative embodiment, the method comprises forming aplurality of word line structures, forming a digitline contact, at leasta portion of which is positioned between the word line structures,forming a plurality of storage node contacts comprising a firstconductive portion and a second conductive portion, the first conductiveportion being in direct contact with a semiconducting substrate, thesecond conductive portion being positioned above the first conductivecontact, wherein there is a conductive interface between the first andsecond conductive portions, the first conductive portion comprising aportion that is positioned between one of the word line structures and apassing word line structure, and forming a liner comprising a low-kdielectric material having a dielectric constant less than 7 adjacent atleast a portion of a side of the second conductive portions.

In one illustrative embodiment, the device comprises a plurality of wordline structures, a digitline contact, at least a portion of which ispositioned between the word line structures, a plurality of storage nodecontacts, each of which comprises a portion positioned between one ofthe word line structures and an adjacent passing word line structure,and a liner comprising a low-k dielectric material having a dielectricconstant less than 7 positioned adjacent at least a portion of a side ofeach of the storage node contacts.

In another illustrative embodiment, the device comprises a plurality ofword line structures, a digitline contact, at least a portion of whichis positioned between the word line structures, a plurality of storagenode contacts comprising a unitary conductive structure, each of thestorage node contacts comprising a portion positioned between one of theword line structures and an adjacent passing word line structure, and aliner comprising a low-k dielectric material having a dielectricconstant less than 7 positioned adjacent at least a portion of a side ofthe unitary conductive structure.

In yet another illustrative embodiment, the device comprises a pluralityof word line structures, a digitline contact, at least a portion ofwhich is positioned between the word line structures, a plurality ofstorage node contacts comprising a first conductive portion and a secondconductive portion, the first conductive portion being in direct contactwith a semiconducting substrate, the second conductive portion beingpositioned above the first conductive contact, wherein there is aconductive interface between the first and second conductive portions,the first conductive portion being positioned between one of the wordline structures and an adjacent passing word line structure, and a linercomprising a low-k dielectric material having a dielectric constant lessthan 7 positioned adjacent at least a portion of a side of the secondconductive portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1 is an illustrative simplified schematic depiction of a DRAM cell;

FIG. 2 is an illustrative schematic depiction of an illustrative DRAMdevice and its associated circuitry;

FIG. 3 depicts a partially formed memory devices in accordance with oneaspect of the present invention;

FIG. 4 depicts the structure of FIG. 3 with a hard mask layer and afirst masking layer formed thereabove;

FIGS. 5-7 depict an illustrative embodiment of a first partial etchingof the hard mask layer;

FIGS. 8-10 depict an illustrative embodiment of a second partial etchingof the hard mask layer;

FIGS. 11-12 are plan views of an illustrative hard mask layer formed inaccordance with one aspect of the present invention;

FIGS. 13-14 are cross-sectional side views depicting an illustrativeexample of using the patterned hard mask layer described herein to formdiscrete contact openings for a device;

FIGS. 15-16 depict one illustrative process flow for filing contactopenings formed in accordance with the present invention;

FIGS. 17-18 depict yet another illustrative process flow for filingcontact openings formed in accordance with the present invention;

FIGS. 19-22 depict one illustrative technique for forming storage nodecontacts in accordance with one illustrative aspect of the presentinvention; and

FIGS. 23-24 depict yet another illustrative technique for formingstorage node contacts in accordance with one illustrative aspect of thepresent invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present invention will now be described with reference to theattached figures. Although the various regions and structures of asemiconductor device are depicted in the drawings as having veryprecise, sharp configurations and profiles, those skilled in the artrecognize that, in reality, these regions and structures are not asprecise as indicated in the drawings. Additionally, the relative sizesof the various features and doped regions depicted in the drawings maybe exaggerated or reduced as compared to the size of those features orregions on fabricated devices. Nevertheless, the attached drawings areincluded to describe and explain illustrative examples of the presentinvention. The words and phrases used herein should be understood andinterpreted to have a meaning consistent with the understanding of thosewords and phrases by those skilled in the relevant art. No specialdefinition of a term or phrase, i.e., a definition that is differentfrom the ordinary and customary meaning as understood by those skilledin the art, is intended to be implied by consistent usage of the term orphrase herein. To the extent that a term or phrase is intended to have aspecial meaning, i.e., a meaning other than that understood by skilledartisans, such a special definition will be expressly set forth in thespecification in a definitional manner that directly and unequivocallyprovides the special definition for the term or phrase.

As will be recognized by those skilled in the art, FIG. 3 depicts aportion of an illustrative memory cell 50 formed above a portion of asubstrate 51 at an intermediate stage of manufacture for an illustrativeDRAM device. The present invention is disclosed in the context ofmanufacturing an illustrative DRAM device. However, as those skilled inthe art will recognize after a complete reading of the presentapplication, the present invention is not limited to the manufacture ofsuch devices, as other types of devices may be manufactured using themethods and techniques disclosed herein.

As shown in FIG. 3, the memory cell 50 comprises a plurality ofisolation regions 54, and an active area 52. Also depicted in FIG. 3 area plurality of access devices 53 (designated as 53 a and 53 b), e.g.,word lines, and a plurality of passing word lines 53 c. As will beunderstood by those skilled in the art, the access devices 53 may be“buried” type devices that are formed in the substrate 51, or they maybe more traditional unburied access devices that are formed above thesurface of the substrate 51. In the illustrative examples depictedherein, the access devices 53 are depicted as unburied access devices.Of course, the present invention may be employed with both buried andunburied access devices. Moreover, the exact configuration of the accessdevices 53 may also vary and should not be considered a limitation ofthe present invention. For example, the access devices 53 may comprise agate insulating layer 57 a, a conductive layer 57 b, a metal silicidelayer 57 c, a top insulating layer 57 d, such as, for example, a layerof silicon nitride, and a sidewall spacer 57 e.

FIG. 3 also depicts a first insulating layer 56 formed above thesubstrate 51. The first insulating layer 56 may be comprised of avariety of materials, e.g., silicon dioxide, BPSG, etc. The first layerof insulating material 56 may be formed by performing any of a varietyof known deposition processes, e.g., chemical vapor deposition (CVD),plasma enhanced chemical vapor deposition (PECVD), etc. Typically, thefirst layer of insulating material 56 will be deposited such that itssurface 58 extends above the surface 59 of the access devices 53.Depending upon the planarity of the surface 59 of the as-deposited layer56, additional planarization processes, e.g., chemical mechanicalpolishing (CMP) process, may not need to be performed on the surface 58of the layer 56. In the illustrative embodiment depicted in FIG. 3, aCMP process has been performed to planarize the surface 58 therebymaking the surface 58 of the first insulating layer 56 substantiallyplanar with the surface 59 of the access devices 53.

Next, as shown in FIG. 4, a hard mask layer 60 is deposited above thestructure depicted in FIG. 3. The hard mask layer 60 may be comprised ofa variety of materials, and it may perform a variety of functions. Asdescribed more fully below, the hard mask layer 60 will ultimately bepatterned and used as an etch mask in defining openings in the firstinsulating layer 56 for conductive contacts for the finished device. Thehard mask layer 60 may also serve other purposes, e.g., it may act as ananti-reflective coating layer. Thus, in prior art processingmethodologies, the hard mask layer 60 may be referred to as a DARC(which may refer to a deposited anti-reflective coating or a dielectricanti-reflective coating). The hard mask layer 60 may be comprised of avariety of materials, other than photoresist materials, and it may beformed using a variety of techniques. Moreover, the thickness of thehard mask layer 60 may vary depending upon the particular application.In general, the hard mask layer 60 is comprised of a non-photoresistmaterial that is selectively etchable with respect to the underlyinginsulating layer 56. Illustrative materials for the hard mask layer 60include, for example, silicon nitride, silicon oxynitride, carbon, etc.The hard mask layer 60 may be formed by, for example, performing a CVDprocess, and it may have any desired thickness, e.g., 700-2000 Å. Thus,particular details of the illustrative hard mask layer 60 depictedherein should not be considered a limitation of the present invention.

As will be described with reference to FIGS. 4-11, the hard mask layer60 will be patterned by performing first and second partial etchingprocesses using first and second masking layers 62, 64. The first andsecond masking layers 62, 64 may be comprised of a variety of materials,e.g., photoresist. As will be recognized by those skilled in the artafter reading the present application, the order in which the maskinglayers 62, 64 and the associated etching processes are described hereinmay be reversed.

FIGS. 4-9 will now be discussed. For purposes of clarity, not allaspects of the illustrative memory cell 50 will be shown in thesedrawings so as to not obscure the present invention. The first patternedmasking layer 62 is formed such that its features 62 a are parallel toand are positioned above the access devices 53. A first etching process,such as an anisotropic etching process, as indicated by the arrows 68,is performed to partially etch the hard mask layer 60, thereby definingrecesses 66, e.g., trenches, in the hard mask layer 60. Note that theetching process is controlled such that the trenches 66 formed duringthis first etching process do not extend through the partially etchedhard mask layer 60 a. Typically, the first etching process may beperformed such that the trenches 66 have a depth that equalsapproximately one-half of the starting thickness of the hard mask layer60.

Thereafter, the first masking layer 62 is removed, and the secondmasking layer 64 (see FIGS. 8 and 9) is formed above the partiallypatterned hard mask layer 60 a. The second masking layer 64 may also becomprised of a variety of materials, e.g., a photoresist material. Thesecond masking layer 64 is formed such that its features 64 a aresubstantially perpendicular to the features 62 a of the first maskinglayer 62. In this illustrative example, the features 64 a of the secondmasking layer 64 are also substantially perpendicular to the accessdevices 53, e.g., the word lines. As indicated above, the order and/orthe orientation of the first and second masking layer 62, 64 may bereversed.

After the formation of the second masking layer 64, the partially etchedhard mask layer 60 a will be subjected to a second partial etchingprocess, e.g., an anisotropic etching process, as indicated by thearrows 71. The second partial etching process 71 defines a plurality oftrenches 69 (see FIG. 9) that are substantially perpendicular to thetrenches 66 formed during the first partial etching process 68 (see FIG.10). This second partial etching process, like the first partial etchingprocess, is designed such that it will not etch through the entireoriginal thickness of the hard mask layer 60. However, the portions ofthe hard mask layer 60 a that are exposed to both the first and secondpartial etching processes will be removed, thereby defining a pluralityof generally rectangular shaped openings 70 (e.g., 70 a, 70 b, 7 c),thereby exposing the underlying first layer of insulating material 56.

FIGS. 8 and 9 are, respectively, a perspective view and an end viewdepicting the patterned hard mask layer 60 b after it has been subjectedto the first and second partial etching processes described above. FIG.10 is a plan view showing the masking layer 60 b after it has beensubjected to the two partial etching processes described above. FIG. 11is a plan view of the patterned hard mask layer 60 b with the openings70 a, 70 b and 70 c formed therein. For purposes of clarity, theassociated trenches 66, 69 are not depicted in FIG. 11. Also note thatan illustrative rectangular shaped active area 52 is depicted in dashedlines since it is positioned under the patterned hard mask layer 60 b.As shown in the drawings, a plurality of openings 70 (designated as 70a, 70 b and 70 c) are formed in the patterned hard mask layer 60 b. Notethat the openings 70 are generally rectangular or square in shape due tothe methodologies employed herein. However, by referring to the openings70 as having a generally or substantially rectangular or square shape,precise geometric precision is not intended. As will be understood bythose skilled in the art, precise geometric precision in the formationof such features is very difficult to achieve. Also note that aplurality of openings 70 u for adjacent memory cells are also partiallyshown in FIG. 10.

FIG. 12 is directed to an alternative embodiment wherein contactopenings may be formed in the patterned hard mask layer 60 b forcontacts to be formed within the memory array and for contacts formedoutside of the memory array, e.g., in some of the peripheral circuitry.As shown therein, an opening 70 d for a contact to be formed outside ofthe array may be formed in the hard mask layer 60 b at the same time theopenings for contacts within the array, e.g., openings 70 a, 70 b and 70c, are formed in the hard mask layer 60 b. It should be understood thatthe opening 70 d is representative in nature in that it may represent aplurality of openings formed in the area outside of the array. The sizeof the openings 70 d and 70 a, 70 b and 70 c may vary depending on theparticular application.

As described with respect to FIG. 2, a DRAM device is comprised of anarray of memory cells 22 and a vast variety of peripheral circuitry,e.g., addressing circuitry 26, sensing circuitry 24, etc. Many of theseperipheral circuits are formed in portions of the substrate at locationsspaced apart from memory array 22. These peripheral circuits alsocomprise active devices, e.g., transistors, capacitors, resistors, etc.,that require the formation of conductive contacts. In prior art processflows, the formation of the conductive contacts to the peripheralcircuits was done at a different point in time in the process flowrelative to the formation of the conductive contacts within the memoryarray 22. Obviously, such a methodology involved the performance of manyadditional process steps relative to the present invention whereinconductive contacts in both the memory array and conductive contactsoutside of the memory array, e.g., in the peripheral circuits, can beformed at the same time. Thus, the present invention may result in lessprocess steps, thereby improving manufacturing efficiency and reducingcosts. The present invention may also remove various processingconstraints, such as the SON CMP process discussed above. The presentinvention may enable the generation of additional process flows whichmay be more efficient.

After the patterned hard mask layer 60 b is formed, it may be used as amask in an etching process to form discrete contact openings in thememory array and in the regions outside of the memory array if desired.As shown in FIGS. 13 and 14, the patterned hard mask layer 60 b withopenings 70 a, 70 b and 70 c (without the array) and 70 d, 70 e and 70 f(outside of the array) formed therein is used as a mask in an etchingprocess that is used to form contact openings 80 a, 80 b and 80 c(within the array) and 80 d, 80 e and 80 f (outside of the array). Anillustrative device 81, e.g., a transistor, is depicted as part of acircuit located outside of the memory array that contains the memorycells. Of course, the present invention is not limited to use insituations where contact openings are formed both inside and outside ofthe memory array at the same time. That is, contact openings within thearray and outside of the array may be formed at different times. In theillustrative example depicted herein, a digitline contact will be formedin the opening 80 b, storage node contacts will be formed in openings 80a, 80 c and contacts for the gate electrode and source/drain regions ofthe transistor 81 in the peripheral circuit will be formed in theopenings 80 d, 80 e and 80 f. The precise methodology and techniquesused to form the actual contacts may vary depending upon theapplication.

Obviously, the openings 80 a, 80 b, 80 c, 80 d, 80 e and 80 f will havethe general shape as that of the openings 70 a, 70 b, 70 c, 70 d, 70 eand 70 f in the patterned hard mask layer 60 b, i.e., substantiallyrectangular or substantially square. Note that the openings 80 a, 80 b,80 c in the memory array, and openings 80 e and 80 f extend all the wayto the active area 52. The opening 80 d in the peripheral regions mayextend all the way to the substrate 51 as well, or extend down tocontact a device formed in the periphery region, such as a transistor, aresistor, a capacitor, etc.

After the contact openings are formed using the patterned hard masklayer 60 b, the openings in the insulating layer 56 may be filed with aconductive material, e.g., a metal, polysilicon, etc., using a varietyof different process flows. After a complete reading of the presentapplication, those skilled in the art will recognize that any of avariety of different process flows may be employed to form conductivematerial in the openings 80 a, 80 b, 80 c, 80 d, 80 e and 80 f. Forexample, as depicted in FIG. 15, a layer of conductive material 88,e.g., a metal such as tungsten, polysilicon, etc., is deposited acrossthe substrate 51 and in the openings 80 a, 80 b, 80 c, 80 d, 80 e and 80f. Thereafter, a planarization process, such as a chemical mechanicalplanarization process, is performed to remove excess portions of theconductive layer 88 that is positioned outside of the openings 80 a, 80b, 80 c, 80 d, 80 e and 80 f. This results in the formation ofconductive contacts 95 a, 95 b, 95 c, 95 d, 95 e and 95 f that extenddown to the active area 22 and/or device 81 depending upon the contactunder consideration. See FIG. 16. In one illustrative embodiment, thecontact 95 b is a digitline contact and the contacts 95 a and 95 c arestorage node contacts for an illustrative dual bit memory cell 50. Inone illustrative embodiment, the contact 95 d is a contact to the gateelectrode of the transistor 81 and the contacts 95 e and 95 f contactthe source/drain regions of the transistor 81.

FIGS. 17 and 18 depict another illustrative process flow for formingconductive contacts within the openings 80 a, 80 b, 80 c, 80 d, 80 e and80 f. As shown in FIG. 17, a conductive layer 90, e.g., tungsten, isblanket deposited across the substrate 51 and in the openings 80 a, 80b, 80 c, 80 d, 80 e and 80 f. A process layer 91, e.g., a layer ofsilicon nitride, is formed above the conductive layer 90. Using knownphotolithography techniques, a masking layer (not shown) comprised of aphotoresist material is formed above the process layer 91. Thereafter,one or more anisotropic etching processes are performed to essentiallypattern the layers 90 and 91, thereby resulting in the structuredepicted in FIG. 18. Note that the etching process may be performeduntil such time as the conductive layer 90 is recessed within theopenings 80 a, 80 c, 80 d, 80 e and 80 f, thereby defining recessedcontact members 96 a, 96 c, 96 d, 96 e and 96 f. In one illustrativeembodiment, the structure 96 b is a unitary or integral digitlinecontact structure that is contacted to the active area 52. The contacts96 a, 96 c are portions of storage node contacts for an illustrativedual bit memory cell. Subsequent processing steps (not shown) may beperformed to form contacts to the recessed contacts 96 a, 96 c, 96 d, 96e and 96 f. Depending upon the particular process flow selected, contactmay be made to the recessed contact members 96 a, 96 c, 96 d, 96 e and96 f using the same or different conductive material.

Another aspect of the present invention will now be described withreference to FIGS. 19-24. FIG. 19 depicts the device after the hard masklayer 60 b has been employed to define an opening 100A for a digitlinecontact and two openings 100B for storage node contacts. Next, as shownin FIG. 20, a bit line 102 is formed using traditional depositiontechniques. In one illustrative embodiment, the bit line 102 iscomprised of a first layer of conductive material 102A, e.g., tungsten,a second layer of conductive material 102B, e.g., titanium, and a caplayer 102C, e.g., silicon nitride. Of course, a variety of differentmaterials may be employed to form the bit line 102.

Next, as shown in FIG. 21, a patterned masking layer 104, e.g.,photoresist, is formed and an etching process, indicated by arrows 105,is performed to define the digitline contact 106 and a first conductiveportion 107 of the storage node contacts. The etching process 105 may becontrolled to determine how much the first conductive portions 107 arerecessed relative to the upper surface 99 of the word line structures 50a, 50 b.

Thereafter, as shown in FIG. 22, a liner 108 is formed in the opening114. The liner 108 may be formed from a variety of insulating materials,e.g., silicon dioxide, silicon nitride, etc. In one particularlyillustrative embodiment, the liner 108 may be comprised of a low-kdielectric material, i.e., a material having a dielectric constant lessthan 7, i.e., less than the dielectric constant of silicon nitride. Forexample, the liner 108 may be comprised of TEOS, silicon dioxide. In oneembodiment, the liner 108 may have a thickness ranging from 200-400 Åand it may be formed using known conformal deposition techniquesfollowed by an anisotropic etching process to clear the dielectricmaterial from above the upper surface 107A of the first conductiveportion 107. Thereafter, the second conductive portion 109 may be formedabove the first conductive portion 107. A conductive interface 115 isthereby established between the first conductive portion 107 and thesecond conductive portion 109. The first and second conductive portions107, 109 may be formed of the same or different materials. The secondconductive portion 109 may be formed by depositing a layer of conductivematerial, e.g., tungsten, titanium, etc., above the cap layer 102C andin the openings between the liner 108. A planarization process may thenbe performed to remove excess portions of the conductive materialpositioned above the cap layer 102C to thereby define the secondconductive portions 109.

FIGS. 23-24 depict an alternative process flow for an illustrativeaspect of the present invention. As shown in FIG. 23, the etchingprocess 105 that is performed to form the digitline contact 106 iscontinued until such time as the entirety of the conductive material102A is cleared from the openings 100B for the storage node contacts.Next, as shown in FIG. 24, the liner 108 is formed in the openings 100Band a unitary conductive portion 110 is formed to constitute the storagenode contact. The conductive portion 110 may be made of any conductivematerial, e.g., titanium, tungsten, etc., and it may be the same as ordifferent from the material 102A. The process flow depicted in FIGS.23-24 provides a continuous storage node contact, as compared to theprocess flow described in FIGS. 19-22 wherein the storage node contactis comprised of the first and second conductive portions 107, 109.Additionally, in the embodiment depicted in FIGS. 23-24, the liner 108extends along the entire length of the unitary conductive structure 110,whereas, in the embodiment shown in FIG. 22, the liner 108 extends alongthe entire length of the second conductive portion 109.

The present invention is generally directed to a method of formingcontacts for a memory device. In one illustrative embodiment, the methodcomprises forming a layer of insulating material above an active area ofa dual bit memory cell, forming a hard mask layer above the layer ofinsulating material, the hard mask layer having an original thickness,performing at least two partial etching processes on the hard mask layerto thereby define a patterned hard mask layer above the layer ofinsulating material, wherein each of the partial etching processes isdesigned to etch through less than the original thickness of the hardmask layer, the hard mask layer having openings formed therein thatcorrespond to a digitline contact and a plurality of storage nodecontacts for the dual bit memory cell, and performing at least oneetching process to form openings in the layer of insulating material forthe digitline contact and the plurality of storage node contacts usingthe patterned hard mask layer as an etch mask.

In another illustrative embodiment, the method comprises forming a layerof insulating material above an active area of a dual bit memory cell,forming a hard mask layer above the layer of insulating material, thehard mask layer having an original thickness, performing at least twopartial etching processes on the hard mask layer to thereby define apatterned hard mask layer above the layer of insulating material,wherein each of the partial etching processes is designed to etchthrough less than the original thickness of the hard mask layer, thepatterned hard mask layer being comprised of a material that isselectively etchable with respect to the layer of insulating material,the patterned hard mask layer having openings formed therein thatcorrespond to a digitline contact and a plurality of storage nodecontacts for the dual bit memory cell, and performing a single etchingprocess to form openings in the layer of insulating material for thedigitline contact and the plurality of storage node contacts using thepatterned hard mask layer as an etch mask.

In yet another illustrative embodiment, the method comprises forming alayer of insulating material above an active area of a dual bit memorycell, depositing a hard mask layer above the layer of insulatingmaterial, the hard mask layer having a deposited thickness, performingat least two partial etching processes on the deposited hard mask layerto form a patterned hard mask layer, wherein each of the partial etchingprocesses is designed to etch through less than the entire depositedthickness of the hard mask layer, the hard mask layer having openingsformed therein that correspond to a digitline contact and a plurality ofstorage node contacts for the dual bit memory cell, and performing atleast one etching process to form openings in the layer of insulatingmaterial for the digitline contact and the plurality of storage nodecontacts using the patterned hard mask layer as an etch mask.

In a further illustrative embodiment, the method comprises forming alayer of insulating material above an active area of a dual bit memorycell, forming a patterned hard mask layer above the layer of insulatingmaterial, the patterned hard mask layer being comprised of a materialthat is selectively etchable with respect to the layer of insulatingmaterial, the hard mask layer having openings formed therein thatcorrespond to a digitline contact, a plurality of storage node contactsfor the dual bit memory cell and an opening for a contact located in aperipheral circuit located outside of a memory array comprising the dualbit memory cell, and performing a single etching process to formopenings in the layer of insulating material for the digitline contact,the plurality of storage node contacts and the contact for theperipheral circuit using the patterned hard mask layer as an etch mask.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. For example, the process steps set forth above may beperformed in a different order. Furthermore, no limitations are intendedto the details of construction or design herein shown, other than asdescribed in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. Accordingly, the protection sought herein is as set forth inthe claims below.

What is claimed:
 1. A dual bit DRAM memory device, comprising: aplurality of word line structures; a digitline contact, at least aportion of which is positioned between two of said word line structures;a plurality of storage node contacts, each of which comprises a portionpositioned between one of said two word line structures and an adjacentpassing word line structure; and a liner comprising a low-k dielectricmaterial having a dielectric constant less than 7 positioned adjacent atleast a portion of a side of each of said storage node contacts.
 2. Thedevice of claim 1, wherein each of said storage node contacts arecomprised of at least two conductive portions that are formed atdifferent times.
 3. The device of claim 1, wherein each of said storagenode contacts are comprised of a first conductive portion and a secondconductive portion, said first conductive portion being in directcontact with a semiconducting substrate, said second conductive portionbeing positioned above said first conductive portion, wherein there is aconductive interface between said first and second conductive portions.4. The device of claim 3, wherein said first and second conductiveportions are comprised of the same material.
 5. The device of claim 3,wherein said first and second conductive portions are comprised ofdifferent materials.
 6. The device of claim 3, wherein said liner ispositioned only adjacent said second conductive portion of said storagenode contact.
 7. The device of claim 6, wherein said first conductiveportion is positioned between an insulating sidewall spacer formedadjacent said one of said two word line structures and an insulatingsidewall spacer formed adjacent said adjacent passing line structure. 8.The device of claim 1, wherein each of said storage node contacts is aunitary conductive structure.
 9. The device of claim 8, wherein saidliner is positioned adjacent an entire length of said unitary conductivestructure.
 10. The device of claim 1, wherein said liner comprises atleast one of TEOS and silicon dioxide.
 11. The device of claim 4 whereinthe first conductive portion has a maximum width that is equal tomaximum width of the second conductive portion.
 12. The device of claim5 wherein the first conductive portion has a maximum width that isgreater than maximum width of the second conductive portion.
 13. Thedevice of claim 5 wherein the digit line contact is comprised ofmultiple conductive materials, an elevationally innermost of the digitline contact conductive materials being in direct contact with thesemiconducting substrate and being of the same composition as that ofthe first conductive portion, the elevationally innermost of the digitline contact conductive materials being elevationally thicker than firstconductive portion.
 14. The device of claim 13 wherein the elevationallyinnermost of the digit line contact conductive materials is thicker thanthe two word line structures.
 15. The device of claim 14 wherein theelevationally innermost of the digit line contact conductive materialsextends elevationally over the two word line structures.
 16. The deviceof claim 15 wherein the elevationally innermost of the digit linecontact conductive materials is in direct contact with each liner thatis adjacent each of said storage node contacts.
 17. A dual bit DRAMmemory device, comprising: a plurality of word line structures; adigitline contact, at least a portion of which is positioned between twoof said word line structures; a plurality of storage node contactscomprising a first conductive portion and a second conductive portion,said first conductive portion being in direct contact with asemiconducting substrate, said second conductive portion beingpositioned above said first conductive contact, wherein there is aconductive interface between said first and second conductive portions,said first conductive portion being positioned between one of said twoword line structures and an adjacent passing word line structure; and aliner comprising a low-k dielectric material having a dielectricconstant less than 7 positioned adjacent at least a portion of a side ofsaid second conductive portions.
 18. The device of claim 17, whereinsaid liner is positioned adjacent said side of said second conductiveportions for an entire length of said second conductive portions. 19.The device of claim 17, wherein said first and second conductiveportions are comprised of the same material.
 20. The device of claim 17,wherein said first and second conductive portions are comprised ofdifferent materials.
 21. The device of claim 17, wherein said firstconductive portion is positioned between an insulating sidewall spacerformed adjacent said one of said two word line structures and aninsulating sidewall spacer formed adjacent said adjacent passing linestructure.